#define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>
#include<math.h>
int main()
{
    int r = 0;
    double p = 3.14;
    scanf("%d", &r);
    double V = 4 * p * pow(r, 3) / 3;
    printf("%.2f\n", V);

    return 0;
}